How can I make this cinnamon stick material more rough and dusty looking?
You had a solid foundation already with how you set up the procedural textures.  You were mostly there, the main issue with your material is  the cracks are a lighter color and the main surface is the darker color; that's backwards. ;)

All of that color multiplying for the material's foundation is trouble. 
Multiplying black and white is very predictable:  lighter colors become lighter and the darker color become darker.
When multiplying color gradients against color gradients, it's difficult to predict what will happen across the entire range of colors.  

When the main 'crevices' node group that you made is converted to grayscale, and the tones are inverted, it looks more like the desired result.



Here is a tip on getting the color tones closer to the reference image.  When hovering over color fields in Blender, you can press e to access the eye dropper tool.  Now you should be able to click just about anywhere else to sample that color.



In several places, a small Noise texture node group was added and is being used to exaggerate and washout the the various procedural textures.

In one instance, the cracks are darkened and deepened where the noise is darkest.  Towards the end of the material, a similar group is being used to color the surface with darker blobs that show in the reference image.

 

Separating the bump mapping(Material Output Displacement socket) into distinct operations allows you to control the cracks separately from the overall small scale bumpiness.  



One thing that you should always add is a proper sky material, even if it's just a flat color.  The .blend you posted has a sky output node with nothing connected to it.  Even though Cycles is designed to use default settings in conditions like this, it's still a potential error state and it's best to avoid since the environment lighting is a big part of how Cycles colors a scene. 
The attached .blend uses a pure white sky(1.0, 1.0, 1.0).

Here's how things are looking now.  



Here's the .blend.
If you have the Node Wrangler Addon enabled(included with Blender) then you can ctrl-shift-click on the various nodes to isolate them and see what they look like flat shaded using the Viewport renderer.